AOA Forums AOA Forums AOA Forums Folding For Team 45 AOA Files Home Front Page Become an AOA Subscriber! UserCP Calendar Memberlist FAQ Search Forum Home

Go Back   AOA Forums > Hardware > General Hardware Discussion

General Hardware Discussion Hard drives, CD, DVD Monitors, All hardware questions not better served by our other Topics

LinkBack Thread Tools Rate Thread
  #1 (permalink)  
Old 13th May, 2002, 05:17 PM
spirits247's Avatar
Join Date: November 2001
Location: UK
Posts: 106

AGP Aperture, the mystery continues............

I'd say I know quite a few things about PC's, but haven't you noticed now and again those grey areas crop up where everyone seems to fling about advice by word of mouth?

And all this advice is constantly conflicting what you've previously read?

Well AGP aperture size is one of those subjects that I just can't get my head around.

You see, I know what AGP aperture size is, I've read all the advice and technical explanations on the internet a thousand times but still can't reach an overall conclusion to grasp this grey area - everyone shouts out something different!

What instigated this thread? Well, I bought a Geforce GTS 64MB DDR to handle a few rounds of online UT. Previously, I had the AGP aperture set to 64MB for my Matrox G200 and this worked well for the GTS. It should, as this size is enough to hold the address space for the onboard video RAM and provide some space for textures if the onboard 64MB is fully utilised.

The thing I don't understand is that when I set AGP aperture to 128MB, UT noticeable accesses the hard drive a lot more and stutters. When I investigated RAM usage, it was A LOT higher with 128MB aperture than 64MB causing higher swap file usage, and this is the problem I can't get my head around.

I was always under the impression that the system would use the video RAM first (in my case 64MB), then switch to using system RAM for textures up to the amount you've specified for the aperture. That's why this setting isn't that important if you have a large amount of video RAM – it’s unlikely it’ll get used anyway.

My experience however, is that this is not the case. System RAM usage goes way up regardless if texture RAM is full or not, because I can't believe UT is maxing out 64MB of onboard memory and filtering that much info into the system RAM. Is something else is going on?????

From my experience, I'd advise people to set the AGP aperture as low as possible without:

a) Hurting benchmark performance
b) Causing game incompatibility

but set it no lower than the memory you have on your card to allow for address space. It seems setting higher apertures just wastes system RAM as it's used regardless if the cards memory is full or not!


Just what is the real deal with AGP aperture sizes?

Do you have to reinstall windows to address the aperture correctly after changing it, because I can't believe the system memory usage between these two settings when I have 64MB onboard video RAM. It appears something is not working right.

Thanks for anyone's advice. I love to clear this grey area up.
Athlon XP 1.33Ghz 1.6V - 133FSB - 2000rpm Silent Coolers
Epox 8KHA+ KT266A - Crucial 256Mb 2100 DDR 2.5V
Radein 8500 64MB DDR - SBlive
4x Front 2x Rear USB 2.0 Card
Deskstar 180GXP 120GB 8MB cache - SpinPoint SP0411N 40GB Low Profile
Optorite CDRW 52x32x52 - Pioneer DVD 115 16x
SkyHawk 400W PSU - 220W combined
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #2 (permalink)  
Old 13th May, 2002, 07:12 PM
Join Date: September 2001
Posts: 5,957

The rule of thumb (as I'm sure you're 101% aware...) is Set the AGP Aperture to 1/2 (50%) of your system memory/RAM.

If you raise the aperture size and it swaps more, then that tells me you don't have as much system memory free as you think.
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #3 (permalink)  
Old 13th May, 2002, 07:47 PM
Chief Systems Administrator
Join Date: September 2001
Location: Europe
Posts: 13,075

I don't fully understand all of AGP - I don't profess to. However, simply setting the AGP aperture to the largest size might not be such a good idea for a number of reasons.

Firstly, the AGP aperture appears as a seperate set of addresses, EVEN THOUGH IT'S THE SAME PHYSICAL RAM! If you have 128Mb of RAM, and an aperture size of 128Mb, the system will allocate enough caching to handle 256Mb of RAM, increasing the usage of your RAM, despite the fact you haven't actually got any more RAM.

In Win9x machines, this causes problems, as the virtual address table for 512Mb RAM, coupled with the 128Mb aperture size means that VCache might run out of virtual addresses to use before finishing allocating virtual addresses to hardware. Obviously this is NOT a good state of affairs!

In NT based machines, the caching system can handle far more RAM, but still you'll lose RAM to the increased cache size.

Secondly, if your card has a large amount of RAM, you don't need such a large AGP aperture, as it's less likely to use any. The "rule of thumb" about setting it to half the RAM is invalid anyhow.

You can't have an AGP aperture less than 16Mb, as control structures that go with it are around 12Mb in size. This is why setting it less than 16Mb means you drop out of AGP mode.

Tuning the AGP aperture looks to be pretty badly documented. It looks like you'll have to run your favourite games, and bring the AGP aperture down until it starts to eat into your frame rate. The less memory you have on your card, the quicker this will happen!

Any views, thoughts and opinions are entirely my own. They don't necessarily represent those of my employer (BlackBerry).
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Mystery graphics card ajopz Graphics and Sound cards; Speakers and other Peripherals 28 29th December, 2006 10:21 PM
Mystery WUs RussianMissile1 ThunderRd's AOA FOLDING@HOME Team 2 10th June, 2004 10:46 PM
AGP aperture size ? Neoprene Graphics and Sound cards; Speakers and other Peripherals 4 8th October, 2003 12:26 AM
Mystery of the On/Off Button patrizio EPoX MotherBoards 17 29th July, 2003 03:19 PM
8rda+ aperture size problem...pc: 26 nfin1te EPoX MotherBoards 3 22nd February, 2003 06:48 PM

All times are GMT +1. The time now is 01:46 PM.

Copyright ©2001 - 2010, AOA Forums
Don't Click Here Don't Click Here Either

Search Engine Friendly URLs by vBSEO 3.3.0